U.S. patent number 5,920,997 [Application Number 08/901,760] was granted by the patent office on 1999-07-13 for automatically retractable chalk line device.
Invention is credited to Michael L. Girtman.
United States Patent |
5,920,997 |
Girtman |
July 13, 1999 |
Automatically retractable chalk line device
Abstract
In accordance with the present invention an automatically
retractable chalk line device is provided having a housing in which
a power spring drives a first large diameter gear through a first
shaft. The first large diameter gear is in driving engagement with
a first smaller diameter gear located below the power spring. The
first smaller diameter gear drives a second large diameter gear
located partially above the power spring. The second large diameter
gear drives a second smaller diameter gear which a drives a chalk
retaining spool, which holds the chalk line. The relative diameters
of the two large diameter gears as compared with the diameter of
the two small diameter gears provides a large mechanical advantage.
A disc brake is mounted for braking engagement with one of the
large diameter gears, preferably the second large diameter gear. An
arrangement for engaging and disengaging the disc brake with the
large diameter gear is provided. This arrangement includes a cam
surface and a slotted plate which is resiliently biased into the
engaged position by the cam surface. A release button is actuated
to move the plate relative to the cam surface to release engagement
between the disc brake and the large diameter gear. The housing for
the chalk line retraction device includes an opening in which a
plate is movable between an open and closed position to allow for
introducing chalk into the assembly adjacent to chalk line. The
housing is provided with an exit portion where the chalk line exits
and an anchor is provided at the end of the chalk line. The strong
power spring and the mechanical advantage achieved from the dual
large gear and dual small gear assembly provides a large mechanical
advantage to enable a longer chalk line of up to a hundred feet or
more to be utilized. The disc brake acting on a large diameter gear
provides very effective braking of the system. The deactivation
device for the brake system is readily accessible and convenient to
operate. Chalk is readily inserted into the housing through sliding
plate assembly for loading and unloading chalk.
Inventors: |
Girtman; Michael L. (O'Fallon,
MO) |
Family
ID: |
25414771 |
Appl.
No.: |
08/901,760 |
Filed: |
July 28, 1997 |
Current U.S.
Class: |
33/414;
242/375.3; 242/385.4 |
Current CPC
Class: |
B44D
3/38 (20130101) |
Current International
Class: |
B44D
3/38 (20060101); B44D 003/38 () |
Field of
Search: |
;33/413,414,767
;242/375.3,381.6,385.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Bennett; G. Bradley
Attorney, Agent or Firm: Cummings; Henry W.
Claims
What is claimed is:
1. An automatically retractable chalk line device comprising: a
power spring mounted for rotation about a first axis; said coil
spring engaging a first vertically extending shaft within said coil
spring and engaging a first large gear; said first large gear being
in driving engagement with a first small gear; said first small
gear being in driving engagement with a second vertically extending
shaft; said second shaft being in driving engagement with a second
large gear; said second large gear being in driving engagement with
a second small gear, laterally spaced therefrom; said second small
gear being in driving engagement with a vertically extending spool
shaft; said spool shaft being integral with a chalk line spool;
said chalk line spool having a chalk line wound about a chalk line
core; said chalk line extending outwardly from said spool and
having means for anchoring said chalk line located outside said
retraction device housing; brake means for maintaining said power
spring in tension position; and means for releasing said brake
means to allow said power spring to drive said first large gear,
said first small gear, said second large gear, said second small
gear, and said spool to retract said chalk line.
2. A device according to claim 1 wherein the said brake means
comprises a disc brake arrangement.
3. A device according to claim 2 wherein said disc brake
arrangement comprises a disc member which engages one of said
gears.
4. A device according to claim 3 wherein said disc member engages
one of said large diameter gears.
5. A device according to claim 4 wherein said means for releasing
said brake system comprises a cam surface and a moveable plate.
6. A device according to claim 5 wherein said moveable plate
contains a slot; said slot in one position is located relative to
said cam surface to provide clearance between said gear and said
disc brake.
7. A device according to claim 6 wherein said plate is activated by
a pivotable release button.
8. A device according to claim 7 wherein said plate contains a
second slot and wherein said manual release button contains a
projection and wherein in braking position said projection engages
said second slot.
9. A device according to claim 8 wherein said release button is
manually activatable to move said plate such that said cam surface
is located within said slot to release said brake.
10. A brake system for a chalk line device comprising; a chalk line
spool containing a chalk line; said spool having a spool shaft
extending outwardly from said spool; said spool shaft engaging a
gear system; said gear system including means for driving said gear
system; said gear system including at least one gear being
engageable with a disc brake to maintain said gear system and said
spool in the braked position.
11. A brake system according to claim 10 wherein said gear
engageable with said disc brake is a large diameter gear.
12. A brake system according to claim 11 wherein means are provided
to engage and disengage said disc brake with said large diameter
gear.
13. A brake system according to claim 12 wherein the means for
causing engagement and disengagement comprises a cam surface and a
movable plate.
14. A brake system according to claim 13 wherein said movable plate
contains a slot and wherein means are provided for moving said
plate into a position whereby said cam surface is located within
said slot and said large diameter gear no longer engages said disc
brake.
15. A brake system according to claim 14 wherein said plate is
movable by a release button.
16. A brake system according to claim 15 wherein release button
engages said slot in said plate when said brake is in brake
position.
Description
FIELD OF THE INVENTION
This invention relates to chalk line devices and in particular to
an automatically retractable chalk line device.
BACKGROUND OF THE INVENTION
U.S. Pat. Nos. 4,197,656 and 4,565,011 disclose automatically
retractable chalk line devices having three independent axis of
rotation. However, neither of these patents locate the shafts on
opposite sides of the device for balance. Furthermore, neither of
these devices utilizes a disc brake which operates on an auxiliary
gear to affect braking of the device.
U.S. Pat. No. 4,121,785 discloses a single axis chalk line device
in which a disc brake assembly is utilized. A push button member 14
integral with the shaft 15 engages projections 18 as a partial disc
brake braking arrangement. However, in the '785 Patent the disc
brake arrangement does not act on a separate auxiliary gear.
SUMMARY OF THE INVENTION
A. Objects of the invention
One object of the present invention is to provide an automatically
retractable chalk line device, in which a chalk line of greater
length may be utilized.
Another object of the present invention is to provide a three axis
design in which the axis's are selected to provide balance in the
device.
Another object of the present invention is to provide a disc brake
arrangement in which the disc acts on an auxiliary gear.
Another object of the present invention is to utilize large
diameter gears and smaller diameter gears to obtain a high gear
ratio.
Another object of the present invention is provide a convenient to
use brake release assembly.
Other objects will be apparent from the following descriptions and
drawings.
B. Summary
In accordance with the present invention an automatically
retractable chalk line device is provided having a housing in which
a power spring drives a first large diameter gear through a first
shaft. The first large diameter gear is in driving engagement with
a first smaller diameter gear located below the power spring. The
first smaller diameter gear drives a second large diameter gear
located partially above the power spring. The second large diameter
gear drives a second smaller diameter gear which a drives a chalk
retaining spool, which holds the chalk line. The relative diameters
of the two large diameter gears as compared with the diameter of
the two small diameter gears provides a large mechanical advantage.
A disc brake is mounted for braking engagement with one of the
large diameter gears, preferably the second large diameter gear. An
arrangement for engaging and disengaging the disc brake with the
large diameter gear is provided. This arrangement includes a cam
surface and a slotted plate which is resiliently biased into the
engaged position by the cam surface. A release button is actuated
to move the plate relative to the cam surface to release engagement
between the disc brake and the large diameter gear. The housing for
the chalk line retraction device includes an opening in which a
plate is movable between an open and closed position to allow for
introducing chalk into the assembly adjacent to chalk line. The
housing is provided with an exit portion where the chalk line exits
and an anchor is provided at the end of the chalk line. The strong
power spring and the mechanical advantage achieved from the dual
large gear and dual small gear assembly provides a large mechanical
advantage to enable a longer chalk line of up to a hundred feet or
more to be utilized. The disc brake acting on a large diameter gear
provides very effective braking of the system. The deactivation
device for the brake system is readily accessible and convenient to
operate. Chalk is readily inserted into the housing through sliding
plate assembly for loading and unloading chalk.
THE DRAWINGS
FIG. 1 is an exploded perspective view of the automatically
retractable chalk line device of the present invention.
FIG. 2 is a schematic perspective view of the external housing of
the chalk line device of the present invention.
FIG. 3 is a horizontal sectional view looking in the direction of
the arrows along line 3--3 in FIG. 2.
FIG. 4 is a vertical sectional view looking in the direction of the
arrows along line 4--4 in FIG. 2.
FIG. 5A is a partial vertical sectional view illustrating the brake
activating mechanism with the brake in the activated position.
FIG. 5B is a view similar to FIG. 5A with the brake in the
deactivated position.
FIG. 6A is view partial horizontal sectional view illustrating the
movable plate to allow insertion of chalk into the assembly.
FIG. 6B is a vertical sectional view looking in the direction of
the arrows along the line 6B--6B in FIG. 6A illustrating details of
the movable plate assembly.
FIG. 7 is a horizontal sectional view looking in the direction of
the arrows along the line 7--7 in FIG. 8.
FIG. 8 is a vertical sectional view looking in the direction of the
arrows along the line 4--4 in FIG. 2, with the chalk line
removed.
DESCRIPTION OF PREFERRED EMBODIMENTS
The automatically retractable chalk line device of the present
invention is indicated in the drawings generally at 1. The assembly
includes a housing 2, including a housing body portion 3, having a
top surface 4, and a vertical wall 5. The housing 2 includes a
spring enclosure portion 6, including an arcuate portion 7. A
spring cover 38 captures spring 30 and is integral with the arcuate
portion 7 by means of fasteners, integral molding or welding. A
bottom plate 8, including vertical portions 9 & 10 is integral
with the spring cover 38 by means of fasteners, integral molding or
welding.
The housing includes a top assembly 17, including a top member 11,
having downwardly extending sides 12. A spool retainer portion 14,
includes a extension of body portion 3 indicated at 16, a bottom
plate 18, which supports the spool including shoulder 20.
Mechanical fasteners 22 hold the assembly together through openings
23, illustrated in FIG. 3.
A chalk line discharge portion 24 includes downwardly and inwardly
extending walls 26 & 28 terminating in a vertical wall 29,
having an opening 29a which includes a wear guide bushing 15
through which the chalk line exits.
A power spring 30 includes a plurality of coils 32 and a housing
body portion 3 includes a coil retainer 33 (FIG. 3). The spring
includes an inner end 34 which engages a spring shaft, 36 which
extends vertically through the spring 30 and engages a first gear
assembly indicated generally at 40. A spring cover 38, which
consists of a protuding bearing surface 37 is located between the
spring and the gear assembly 40 (FIG. 1).
The gear assembly 40 includes a large gear, 41 having teeth 42,
which engage a small gear 43, having teeth 44 (FIG. 1). Shaft 36
mechanically engages large gear 41 through non-round projection 39
on the shaft and non-round opening 45 on the large gear. Bottom
plate 8 captures the gear assembly in place. The difference in
diameter between large gear 41 and small gear 43 provides a
substantial mechanical advantage.
Small gear 43 includes a non-round opening 46 which receives a
shaft 50, through bearing 47 and housing 2, having a non-round end
portion 51. Vertical shaft 50 includes a non-round upper end
portion 53, which engages a non-round opening 61, in gear assembly
60. Non-round opening 61 is located within a large gear 63 which
has teeth 65 which engages small gear 64 having teeth 67. Small
Gear 64 having a non-round opening receives spool shaft portion 92,
which has a non-round end portion 62, through seal 48 and housing
2. Seal 48 prevents chalk contamination of brake assembly 70.
A brake assembly 70 is provided including a brake pad 72 which in
engaged position engages the large gear surface 68 and in
disengaged position is spaced therefrom as illustrated in FIGS. 1
and 5B. The brake pad 72 is integrally connected to top cover 11
and is nonmoveable. Gear assembly 60 is provided with limited
vertical movement on shaft 50 to provide the relative movement
between brake pad 72 and gear 63.
A brake activating assembly 73 includes a horizontally moveable
plate 74 which is movable over a cam surface 75 located on
horizontal housing surface 76. Plate 74 includes an opening 77 for
passage of spool shaft 92 to engage small gear 64. A pair of
resilient springs 78 held in place with spring cavity 84, within
rectangular wall housing 79 resiliently bias a release button 80
into a position wherein button release projection 82 engages an
opening 83 in plate 74 to maintain the plate 74 and gear 63 in the
engaged position with disc 72. Release button 80 rotates about
pivot shaft 86, which is captured across rectangular wall housing
79.
The spool assembly indicated generally at 90 includes a upper spool
shaft 92 extending upwardly from an upper plate 94 and a lower
spool shaft 87 extending downwardly from bottom plate 96. A spool
core 95 extends between upper plate 94 and bottom plate 96 to hold
the chalk line 100 in place. Upper spool shaft 92 engages housing 2
through circular hole 88 of top surface 4. Lower spool shaft 87 is
integral with bottom plate 18, allowing free rotation. Upper plate
94 and bottom plate 96 fit within formed shoulders 97 and 98,
guiding chalk line 100 inside upper plate 94 and bottom plate
96.
The chalk line 100 passes between chalk line retainers 102 and 104
then through wear guide bushing 15 connecting to an anchor 106 by
the use of a knot 105. The housing 2 includes an opening 110 as
illustrated in FIG. 6A for insertion of chalk. A plate 112 is
mounted for movement back and forth to open and close this opening.
The plate includes a projection 114 for moving the plate back and
forth. The plate is also provided with another projection 116 which
engages a slot 118 in the housing to maintain the plate in the
closed position.
To open the housing to receive chalk the projection 114 is grasped
and sufficient force is provided to overcome the interference fit
with the projection 116 and the slot 118 and plate 112 is moved
from right to left in FIG. 6A.
FIG. 5A shows the brake assembly 70 in the engaged position in
which the brake pad 72 is in engagement with the surface 68 on the
large gear 61. In this position the manual release button 80 is in
the position shown with the projection 82 located within the plate
slot 83.
To release the brake, the manual release button 80 is rotated with
the grip portion 85 in a clockwise direction against the bias of
the spring 78. This forces the plate 74 from right to left so that
the slot 77 is located upon the cam 75 and thereby allowing
clearance between the brake pad 72 and the large gear surface
68.
In the operation of the automatic retractable chalk line device, to
fill the device with chalk, the plate 112 is moved from right to
left in FIG. 6A and the chalk is then poured into the housing
through opening 110 so as it will engage the chalk line 100 as the
chalk line exits the housing. After filling the housing the plate
is moved from left to right in FIG. 6A until the projection 116
engages the slot 118 to hold the plate in the closed position. The
anchor 106 is connected to a suitable anchor position in line with
the chalk line to be prepared. The operator then moves from right
to left in FIGS. 1 to 4 and in so doing the chalk line is rotated
about the core 95 to extend the chalk line. In so doing the power
coil spring 30 is tensioned. When the chalk line has been removed
sufficiently to draw the line for the distance desired, the line is
snapped in a manner similar to engaging a string instrument and the
chalk forms the desired line.
To retract the line, the manual release button 80 is pivoted in a
clockwise direction by the operator engaging the grip portion 85
and the plate 74 moves from right to left in FIGS. 5A and 5B
whereby the cam surface 75 is located within the slot 77 of the
plate, providing clearance between the brake pad 72 and the large
gear 61. The power coil spring 30 is then free to unwind within the
housing. This results in shaft 36 driving large gear 41 and small
gear 44. Small gear 44 in turn drives shaft 53 and large gear 61.
Large gear 61 drives small gear 64. Small gear 64 in-turn drives
the spool shaft 92, which causes the chalk line 100 to be rotated
back into the loaded position.
The advantages of the present invention are apparent. In the first
place the chalk line is fully retractable through the action of the
power coil spring and driven gears. Secondly, the disc brake 72
acting on the large gear 61 provides extremely effective disc brake
arrangement. Thirdly, the large difference in diameter between the
respective gears, 41 and 44, and 61 and 64 provides a large
mechanical advantage for the gear system. Fourth, the location of
the three shaft axis 36, 50 and 92 provide a balanced arrangement
within the housing to allow centered point 99 to be used as a blumb
bob. Fifth, the location of the two sets of gears, one in the lower
portion of the housing 41, 43 and the location of the second gear
arrangement 61, 64 in the upper portion of the housing provides
further balance for the chalk line device. Sixth, with the
arrangement of the present invention, the chalk line length of 100
feet can be utilized, it is believed this represents a significant
distance improvement over prior art chalk line devices.
As an example, the power coil spring has a diameter of 3 inches,
and is 1/64 inch in thickness. Large gears 41 and 61 conveniently
have a diameter of 2 and 9/16 inches and small gears 44 and 64
conveniently have a diameter of 15/16 inch.
* * * * *